We hope to determine whether any clinial characteristics of patients with acute psychoses will predict the likelihood of their responding to lithium as opposed to neurolepic treatment. We propose to study a population of newly admitted psychotic inpatients, who have varying amounts of affective symptomatology (using considered characteristic of manic-depressive illness) and cognitive symptomatology, such as disordered thinking, delusions, and hallucinations (usually considered characteristic of schizophrenic illness). They will be randomly assigned to lithium carbonate or to chlorpromazine for a three-week, double-blind trial. We will attempt to find subgroups of the patient population, or combinations of clinical factors, for which the response to the two drugs is different. The results should be of value to the clinician treating such patients, and also of theoretical interest in clarifying the nature of psychotic symptomatology. In a non-blind follow-up period of one year, the longer-term therapeutic or adverse effects of the two drugs will be compared.